Lyman-alpha blob 1

Lyman-alpha blob 1
interstellar cloud
Intergalactic cloud

Polarized image of LAB-1, shown as the faint, green gas cloud.
Credit: Very Large Telescope, European Southern Observatory
Observation data: J2000 epoch
Subtype Lyman-alpha blob
Right ascension 22h 17m 25.97s[1]
Declination +00° 12′ 38.9″[1]
Distance 1.15 × 1010 ly
Constellation Aquarius
Physical characteristics
Radius 300,000 ly
Designations SMM J221726+0013[1]

Lyman-alpha blob 1 (LAB-1) is a giant cosmic cloud of gas located at the southern constellation of Aquarius, some 11.5 billion light-years from Earth with a redshift (z) of 3.09. It was discovered unexpectedly in 2000 by Charles Steidel and colleagues,[2] who were surveying for high-redshift galaxies using the 200 inch (5.08 m) Hale telescope at the Palomar Observatory.[3] The researchers had been investigating the abundance of galaxies in the young Universe when they came across two objects which would become known as Lyman-alpha blobs[2]—huge concentrations of gases emitting the Lyman-alpha emission line of hydrogen.[4]

Left: Lyman alpha blob-1 as seen in Lyman-alpha (yellow), infrared (red) and ultraviolet (blue). The round blue object at the upper left of the blob is a giant galaxy. Right: Artist's impression of how the blob may look like if viewed from relatively close.

LAB-1 is the first discovered Lyman-alpha blob, hence it has the number 1. It is the prototype of objects of this kind.[3] It is also the largest of its kind, measuring 300,000 light years across, three times larger than the Milky Way.[4] The blob appears green on the image because of the combination of the high redshift (z = 3) and the ultraviolet nature of the blob.[4] Imaging with the European Southern Observatory's Very Large Telescope showed that much of the light from the blob is polarized, the proportion increasing and peaking at around 20% at a radius of 45 kiloparsecs (145,000 light-years), forming a huge ring around the blob.[5]

It is still unclear as to why this object is emitting the Lyman-alpha emission radiation. It is thought that the light is coming from galaxies within the central region of the blob. Light of such intensities could be from active galaxies or supermassive black holes actively absorbing matter.[4] An alternate theory is that the light is from cooling gas falling into early galaxies, which has possibly come from cosmic filaments (as galaxies are thought to form at the intersections of these filaments), however the pattern of polarisation found argues against this.[2]

References

  1. ↑ 1.0 1.1 1.2 "SIMBAD Astronomical Database". Result for SMM J221726+0013.
  2. ↑ 2.0 2.1 2.2 Bower, Richard (2011). "Unlocking the Secrets of the Giant Blobs". Nature 476 (3760): 288–89. Bibcode:2011Natur.476..288B. doi:10.1038/476288a. ISSN 0028-0836.
  3. ↑ 3.0 3.1 Steidel, Charles C.; Adelberger, Kurt L.; Shapley, Alice E. (2000). "Lyα Imaging of a Proto–Cluster Region at z = 3.09". Astrophysical Journal 532: 170–82. arXiv:astro-ph/9910144. Bibcode:2000ApJ...532..170S. doi:10.1086/308568.
  4. ↑ 4.0 4.1 4.2 4.3 "Giant Space Blob Glows from Within". ESO Press Release. 17 August 2011. Retrieved 18 August 2011.
  5. ↑ Hayes, Matthew; Scarlata, Claudia; Siana, Brian (2011). "Central powering of the largest Lyman-[alpha] nebula is revealed by polarized radiation". Nature 476 (3760): 304–07. arXiv:1108.3332. Bibcode:2011Natur.476..304H. doi:10.1038/nature10320. ISSN 0028-0836.